Electric heater



Jan. 7, 1930. c. P. RANDOLPH 1,742,553

ELECTRIC HEATER Filed May 14,' 1928 Fig.

Inventor: 1" Charles. F? Randolph,

1 Hi5 A-t-tor-neg.

Patented Jan. 7, 1930 UNITED STATES PATENT OFFICE? CHARLES I. RANDOLPH, 0F OAK PARK, ILLINOIS, ASSIGNOR TO EDISON ELECTRIC APPLIANCE COMPANY, INCORPORATED, OF

OF NEW YORK CHICAGO, ILLINOIS, A CORPORATION ELECTRIC HEATER Application filed May 14, 1928.

My invention relates to electric heaters and has for its object the provision of simple and reliable temperature responsive control means for electric'heaters.

More specifically my invention relates to temperature responsive means for opening and closing a heating circuit or a control circuit for a heating circuit, so as to maintain a desired predetermined temperature. Although it obviously has general application to electrically heated devices, my invention is particularly useful in connection with electric flat irons.

In carrying m invention into effect in one form thereo I provide a bimetallic thermostat for operating the circuit controlling means so as to maintain a substantially constant predeterminedtemperature. I further provide adjusting means whereby the temperature setting of the control means may be changed'as desired so that a temperature will be maintained which is suitable for the particular conditions of operation. This adjusting means in one form comprises a member freely operable fromthe exterior of the device and cooperating with the ther mostat so as to vary its position and hence.

its temperature setting. As applied to a fiat iron, for example, the thermostatic control means may be adjusted tomaintain a desirable low temperature for light fabrics, a higher temperature for medium work and a still higher temperature for heavy work, these various adjustments being easily and quickly made during the operation of the iron as each class of work is encountered.

My invention also comprehends temperature adjustment means having an infinite number of steps whereby any desired temperature setting maybe made, and further- 'more a temperature adjustment member.

shown as an arm, conveniently located with relation to the handle of the iron so-that it may be moved by the hand of the operatorwhile'still grasping the handle of the iron.

For a more complete understanding of my invention reference should be had to-the ac companying drawing in which: Figure 1 is a vertical sectional view of an electric flat iron provided with a temperature control Serial No. 277,423.

device embodying my invention, showing the control devlcein its closed posltion; Figure 2 is a plan view of the electric fiat iron with the cover removed; Figure 3 is a view simiis cast a suitable electric heating unit 11. As

shown, the upper portion of the body member 10 is enclosed by a cover 12 resting on a shoulder 10 provided for it, the cover12 being suitably secured to the body member 10 by means of screws (not shown).

In the upper portion of body member 10 is an elongated recess 13 in which is secured a temperature-responsive control device for the heating unit 11. The temperature control device comprises a suitable thermostat, shown as a bimetallic bar 14 made of two strips of metal such a invar and Monel metal, these two strips being securely welded or brazed together lengthwise. The thermostat 14 is rigidly secured at one end to the body member 10 by means of a clamping screw 15 passing througha suitable hole provided for it in the bar. It will be observed that the thermostat 14 is secured within the lower portion of the recess 13 adjacent the working surface of the iron so that heat may be transmitted directly to the thermostat from the working surface. In order to as nearly as practicable distribute the fibre stresses uniformly in the thermostatic metal'and thus reduce the maximum fibre stresses, the fixed end of the ther-' the opposite or movable end, and in order to prevent curving of the thermostat in a direction at right angles to the desired movement-of the thermostat, the thermostat is provided with a longitudinal slot 14. Upon distoition of the thermostat, due to changes in temperature, the unsecured or free end moves laterally.

This movable end of the thermostat 14 is provided with a. knife-edge pivot bearing 16 which rests in a bearing seat provided for it in one arm of an inverted U shaped resilient member or spring 17. The other arm of the spring 17 is seated on a fixed knife-edge bearing 18, the seats for the knife-edge bearings 16 and 18 being provided by striking V shaped indentations in the ends of the two arms of the member 17 as shown'in Figures 1 and 3.

A temperature adjustment rod or shaft 20 is provided for enabling-the iron to be operated at any desired predetermined temperature. The rod or shaft 20 is in screwthreaded relation at its lower end with the body member 10, and extends upwardly through an opening provided in the thermostat 14. A pair of nuts are threaded upon the rod or shaft 20 and provide a ,stop or abutment 21 for the thermostat 14, which is resilient to a considerable degree and normally bears against the abutment 21. A stop 21 constituting an upper limiting position for the nuts is formed upon shaft 20. The rod or shaft 20 engages the thermostat a short distance away from the point of attachment of the thermostat to the body member 10. As shown, this point of engagement is somewhat less than one-half the distance from the point of support to the end of the thermostat. The upper end of the rod or shaft 20 protrudes from the cover 12 of the iron and is provided with a handle or knob 22 whereby the rod may be turned to raise or lower it, so that the thermostat-may be flexed and its free end thus raised or lowered to change its temperature setting. The upper portion of the rod 20 is provided with" a chamtered head 20 fitted within a recess 22 provided in the handle 22, the recess 22 having a cross section corresponding with that of the head 20,. The handle 22 is further provided with a cylindrical member 22 which has outwardly turned ears 22 which will engage the cover 12 to secure the handle 22. The cylindrical member 22 also constitutes an upper bearing for the shaft 20. Thus it will be observed that the handle 22 may be rotated to raise or lower the rod or shaft 20. It will be understood that the thermostat 14 is normally depressed by the abutment 21 so that when the rod 20 1S moved upward, the thermostat springs upward, its temperature setting being thereby changed. A support 29 for preventing lateral displacement of the adjusting shaft 20 is secured to the body member 10.

The bearing 18 lies in the plane of movement of the thermostat 14 and the arrange ment of the thermostat is such that at a predetermined temperature the knife-edge bearing 16 on the thermostat will lie on a line passing through the bearing 18 and the e'f fective point of support of the thermostat. This position of the thermostat will be here after referred to as the neutral position.

point of engagement between the thermostat and the abutment 21.

The resilient, member or spring 17 serves to apply a force to the movable end of the thermostat. The arms of the member 17 tend to separate by reason of the resiliency of the member, they being normally compressed somewhat between the bearings 16 and 18, whereby the member exerts a force on the movable end of the thermostat, this force tending to hold the movable end on one side or the other of the neutral position. In the neutral position, however, the entire force exerted by the member 17 is directed lengthwise of the thermostat, but when the end of thermostat moves from the neutral position in either direction, a lateral component of this spring pressure is produced tending to force the thermostat from its neutral position. This lateral component increases as the thermostat moves away from the neutral position.

Secured to the base portion of the memher 17 are two springs, a lower spring 23 and an upper spring 24, a washer 25 being inserted between the springs. Rivets 26 serve to secure the springs and washer to the member 17. The lower spring 23 constitutes a switch arm and on its free end carries a bridging contact 27. A yoke 28, riveted to the free end of the switch arm 23, serves to support the bridging contact 27 As shown, the mechanical connection between the bridging contact 27 and the yoke 28 is effected by a yoke pin 30. A connector bar 31 interconnects the contacts 32 and 32 (Fig. 5) and an insulator 33 is inserted between the connector bar 31 and the yoke 28. The bridging contact 27 cooperates .with fixed contacts 34 and 34 secured to a supporting bracket 35 in electrically insulated relation therewith and with each other, the bracket 35 being secured to the plate 10 by means of screws 36. The contact 34 is connected by nieans of a conductor 37 and a lead 38 to one terminal 40 of the electric heating unit 11, while the contact terminal 34 may be electrically connected by means of the conductor 41 and the lead 42 to one of a pair of contact pins 44, the other contact pin being electrically connected to the remaining terminal 43 of the heating unit. It will be understoodthat an electrical connection is established between the contact pins 44 .and a suitable supply source by means of a suitable plug connector.

It will be observed therefore, that when as the temperature is below a predetermined maximum temperature. Under this condition, the movable. end of the thermostat is situated below the neutral position. As the temperature increases the distortion of the thermostat tends to move its free end upward, but this movement is resisted by the resilient number 17 Upon the occurrence of the predetermined maximum temperature, however, the thermostat has sufficient force to overcome the spring 17 and starts to move upward. As the thermostat moves upward, the opposing force exerted by the spring 17 decreases, since the spring 17 exerts its force more nearly in the direction of the line of support of the thermostat. The thermostat 14, therefore, rapidly accelerates and moves at high speed through the neutral position to the opposite side thereof, where it is urged rapidly upward by' the increasing lateral component of force applied by the spring 17 1 The heating circuit is thus quickly opened, the bridging contact 27 being thrown upward with a snap action to the position shown in Figure 3 so as to disengage the fixed contacts 34 and 34 This snap'action isfurther assured by the flexible switch arm 23. In the closed circuit position, as shown in Figure 1, the contact arm is bent downward somewhat by reason of the fact that the bridging contact 27 engages the fixed contacts 34 and 34 somewhat before the thermostatic bar 14 reaches its nor mal closed circuit position. As a result of this arrangement the bridging contact is held in engagement with the fixed contacts 34 and 34*, by reason of the straightening of the switch arm 23, during the initial movement of the thermostat and this initial slow movement is thus absorbed so that the thermostat has an opportunity to accelerate to a high speed by the time the arm 23 has straightened itself and moves the bridging contact 27 away from the fixed contacts 34 and 34. This arrangement of the flexible switch arm 23 also causes the contacts to move into and out of engagement with a wiping action thereby preventing the accumulation of dirt or other deposits on either the movable or stationary contacts.

After the heating circuit has been opened and the temperature of the device, and conse uently of the thermostat, begins to decrease the distortion of the thermostat tends to move it back to' the closed circuit position, but its movement is opposed by the force exerted by the member 17, this force being overcome at some predetermined minimum temperature when the thermostat 17 will snap to closed circuit position, shown in Figure 1. Thus, the heating circuit is controlled so as to maintain a predetermined temperature which is a mean between the maximum and minimum temperatures for which the device is set to oper ate. During the closing of the circuit the arm 23 bends downward after the engagement of the contacts.

When the switch arm 23 is in the open cir- I cuit position it comes to rest againstthe cover 12, asshown in Figure 3, and when the control devlce is in closed circult position, as 1nd1- ,cated in Figure 1, the thermostat is free to bend downward in response to relatively low temperatures when the heating device is not used. \Vhile downward movement of the thermostat is opposed by the switch arm 23,

this opposition is more than balanced by the force applied by the spring 17. The thermostat is then free to take up any position due to distortion at low temperatures, and conse quently there is no danger of permanent dis- .tortion of the thermostat due to stresses that might be set up if its freedom of distortion were restricted by the switching mechanism.

By means of the adjustment rod or shaft 20, the device can be set to maintain a desired pre determined temperature. By turning the handle or knob 22 so as to turn the shaft 20 downward, the device is set to maintain a higher temperature, whereas to decrease this temperature the handle 22 is moved to turn the shaft 20 upward. Preferably an indicating dial 22 (Fig. 4) with which the handle 22 cooperates is placed upon the cover 12, whereby any desired temperature adjustment may be easily and accurately made the temperature adjusting means having an infinite number of steps. It will be observed that the handle 22is in such position that it may be readily turned by the operator as the ironing proceeds with his hand still grasping the handle 12 of the iron.

It will be observed that the bearing 18 is carried by a cylindrical member 19 loosely fitted within the bore 19*, thus permitting the set screw 47 to be rotated without rotating the bearing 18. By turning the screw 47, so as to move the bearing 18 inward against the spring 17, that is, toward the right, as viewed in Figures 1 and 3, the force exerted by the spring 17 is increased and, therefore, the.

1,367 ,341 to Abbott, dated February 1, 1921. This unit comprises an outer metallic sheath 45, suitably shaped in which a helical heating resistor 46 is embedded inpowdered heat refractory insulating material 47. The heating unit is shaped roughly in the form of a horse shoe as shown in Figure 2.

While I have described my invention as embodied in concrete form and as operating in a specific manner is accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modifications thereof will suggest themselves to those skilled in the the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is 1. An electrically heated device comprising a body member an electric heating unit therefor, a bimetalhc bar thermostat secured at one end to said body member and havin its other end free, control means for said 515 heating unit operated by said thermostat, a cover for said thermostat and control means, said cover being secured to said body member, and a rod in threaded engagement with said body member and cooperatin with said thermostat so as to vary its position upon rotation of said rod and thereby vary the temperature setting, said rod projecting from said cover whereby it may be adjusted from the exterior of the iron. 2. An electrically heated. device comprismg a body member, an electric heater for said body member, a contact arm mounted u on said body member, a thermostat arrange to actuate said contact arm for opening and closing the circuit of said heater, a rod threaded into said body member, means operable from the exterior of said iron for turnmg said rod, and means cooperating with said thermostat and actuated by said rod for altering the temperature of actuation of said contact arm by said thermostat.

\ 3. An electrically heated flat iron comprising, a body member, a cover for said body member, a contact supporting arm mounted upon said body member, a resilient apertured thermostat arranged to actuate said contact arm for opening and closing the circuit of the iron, a shaft threaded into said body member extending through said aperture and projecting from said cover whereby said shaft may be adjusted from the exterior of the iron, and an abutment upon said shaft against which said themostat rests.

4.. In an electrical flat iron, a body memher having a recess therein, an electric heater for said body member, a contact supporting arm mounted in said recess, a thermostat within said recess in thermal relation with the working surface of-the iron and arranged to actuate said contact supporting arm to art without departing from the spirit of myinvention, the scope of which is set forth in open and close the iron circuit. a rod controllable from the exterior of said iron extending through said recess and threaded into said body member, and operable connections between said thermostat and said rod whereby the action of said thermostat may be varied by turning the rod.

5. In combination, an electric iron, a thermostat arranged within said iron in thermal relation with the working face thereof, a resilient member bearing on said thermostat so as to cause said thermostat'to snap quickly from one postion to another, an electric circuit controlling member carried by said resilient member, and means controllabh; from the exterior of said iron for modifying the action of said thermostat.

6. The combination in an electric llat iron of a flat iron body member having an upper recess therein, an electric heater for said body member, a thermostat in said recess having one end secured to said body member, a fixed pivot bearing adjacent the movable end of said thermostat, a resilient member bearing on said fixed pivot and the movable end of said thern'iostat, a contact arm carried by said resilient member, and control means adjustable from the exteriot of said flat iron for modifying the action of said thermostat.

7. Thermostatic control means for electric heaters and the like comprising a body member, circuit control means, a resilient thermostat for operating said control means so as to ,maintain a substantially constant predetermined temperature, a rod in threaded engagement with said body member and provided with an abutment against which said thermostat rests, and means for moving said rod whereby the position of said abutment is changed so as to vary thetemperature setting of said thermostat.

8. A temperature control device comprising a su-p ort, a thermostat secured at one end to sai support, a resilient member hearing on said thermostat so as to cause said thermostat to snap quickly-from one position to another, an electric circuit controlling memberv carried by said resilient member, and a shaft screw threaded into said support'and operably connected to said thermostat for varying the temperature of actuation of said circuit controlling member by said thermostat.

9. The combination with an electric flat iron provided with a body member having a recess therein, of a thermostat in said recess in thermal relation with the working surface of the iron and having one end secured to said body member, a fixed pivot bearing within said recess adjacent the movable end of said thermostat, a resilient member within said recess and projecting upwardly therefrom hearing on said fixed pivot and the movable end-of said thermostat, :1. comm-t arm carried by the projecting portion of said re silient member, a shaft screw threaded into said body member extending upwardly through said recess and controllable mm the exterior of the upper portion of the iron, and means cooperating with said thermostat and actuatedby said shaft for modifying the action of said thermostat.

. prising a body member, a handle for said iron, an electric heater for said body member, a contact arm mounted upon said body member, a thermostat arranged to actuate said contact 'arm for opening and closing the circuit of said heater, a rod threaded into said body member, means cooperating with said thermostat and actuated by rotation of said rod for altering the temperature of actuation of said contact arm by said thermostat, and an arm operable from the exterior of said iron for rotating said rod, said arm being so positioned that it may be readily manipulated by the fingers of the hand engaging saidhandle. V

In Witness whereof, I have hereunto set my hand this 8th day of May, 1928.

CHARLES P. RANDOLPH.

10. An electrically heated flat iron com- 

